#include <stdarg.h>
#include <string.h>

#define is_digit(c) ((c) >= '0' && (c) <= '9')
	
static int skip_atoi(const char **s) {
    int i=0;
	
    while (is_digit(**s)) {
        i = i*10 + *((*s)++) - '0';
    }
	
    return i;
}
	
#define ZEROPAD 1       /* pad with zero */
#define SIGN    2       /* unsigned/signed long */
#define PLUS    4       /* show plus */
#define SPACE   8       /* space if plus */
#define LEFT    16      /* left justified */
#define SPECIAL 32      /* 0x */
#define SMALL   64      /* use 'abcdef' instead of 'ABCDEF' */
	
#define do_div(n,base) ({ \
        int __res; \
        __asm__("divl %4":"=a" (n),"=d" (__res):"0" (n),"1" (0),"r" (base)); \
        __res; })
	
static char * number(char * str, int num, int base, int size, int precision
    ,int type) {
    char c,sign,tmp[36];
    const char *digits="0123456789ABCDEFGHIJKLMNOPQRSTUVWXYZ";
    int i = 0;
	
    if (type&SMALL) digits="0123456789abcdefghijklmnopqrstuvwxyz";
    if (type&LEFT) type &= ~ZEROPAD;
    if (base<2 || base>36)
        return 0;

    c = (type & ZEROPAD) ? '0' : ' ' ;
    if (type&SIGN && num<0) {
        sign = '-';
        num = -num;
    }
    else {
        sign=(type&PLUS) ? '+' : ((type&SPACE) ? ' ' : 0);
    }
	
    if (sign) size--;
    if (type&SPECIAL) {
        if (base==16) size -= 2;
        else if (base==8) size--;
    }
	
    if (num==0)
        tmp[i++]='0';
    else {
        while (num!=0) {
            tmp[i++]=digits[do_div(num,base)];
        }
    }
	
    if (i>precision) precision=i;
    size -= precision;
	
    if (!(type&(ZEROPAD+LEFT))) {
        while(size-->0)
            *str++ = ' ';
    }
	
    if (sign)
        *str++ = sign;
	
    if (type&SPECIAL) {
        if (base==8)
            *str++ = '0'; 
        else if (base==16) {
            *str++ = '0';
            *str++ = digits[33];
        }
    }
	
    if (!(type&LEFT)) {
        while(size-->0)
            *str++ = c;
    }
	   
    while(i<precision--)
        *str++ = '0';
	
    while(i-->0)
        *str++ = tmp[i];
	
    while(size-->0)
        *str++ = ' ';
	
    return str;
}
	
int vsprintf(char *buf, const char *fmt, va_list args) {
    int len;
    int i;
    char * str;
    char *s;
    int *ip;
	
    int flags;      /* flags to number() */
    int field_width;    /* width of output field */
    int precision;      /* min. # of digits for integers; max
                           number of chars for from string */
    int qualifier;      /* 'h', 'l', or 'L' for integer fields */
	
    for (str = buf; *fmt; fmt++) {
        if (*fmt != '%') {
            *str++ = *fmt;
            continue;
        } 
       
        /* process flags */
        flags = 0;
        repeat:
            ++fmt;      /* this also skips first '%' */
            switch (*fmt) {
                case '-': flags |= LEFT; goto repeat;
                case '+': flags |= PLUS; goto repeat;
                case ' ': flags |= SPACE; goto repeat;
                case '#': flags |= SPECIAL; goto repeat;
                case '0': flags |= ZEROPAD; goto repeat;
            }
	
        /* get field width */
        field_width = -1;
        if (is_digit(*fmt)) {
            field_width = skip_atoi(&fmt);
        }
        else if (*fmt == '*') {
            field_width = va_arg(args, int);
            if (field_width < 0) {
                field_width = -field_width;
                flags |= LEFT;
            }
        }
	
        /* get the precision */
        precision = -1;
        if (*fmt == '.') {
            ++fmt;  
            if (is_digit(*fmt))
                precision = skip_atoi(&fmt);
            else if (*fmt == '*') {
                /* it's the next argument */
                precision = va_arg(args, int);
            }
	           
            if (precision < 0)
                precision = 0;
        }
	
        /* get the conversion qualifier */
        qualifier = -1;
        if (*fmt == 'h' || *fmt == 'l' || *fmt == 'L') {
            qualifier = *fmt;
            ++fmt;
        } 
	        
        switch (*fmt) {
            case 'c':
                if (!(flags & LEFT))
                    while (--field_width > 0)
                        *str++ = ' ';
                *str++ = (unsigned char) va_arg(args, int);
                while (--field_width > 0)
                    *str++ = ' ';
                break; 
            case 's':
                s = va_arg(args, char *);
                len = strlen(s);
	               
                if (precision < 0)
                    precision = len;
                else if (len > precision)
                    len = precision; 
	                
                if (!(flags & LEFT))
                    while (len < field_width--)
                        *str++ = ' ';
                for (i = 0; i < len; ++i)
                    *str++ = *s++;
                while (len < field_width--)
                    *str++ = ' ';
                break; 
	            
            case 'o':
                str = number(str, va_arg(args, unsigned long), 8,
                        field_width, precision, flags);
                break; 
	            
            case 'p':
                if (field_width == -1) {
                    field_width = 8;
                    flags |= ZEROPAD;
                }
                str = number(str,
                        (unsigned long) va_arg(args, void *), 16,
                        field_width, precision, flags);
                break; 
            
            case 'x':
                flags |= SMALL;
            case 'X':
                str = number(str, va_arg(args, unsigned long), 16,
                        field_width, precision, flags);
                break; 
	            
            case 'd':
            case 'i':
                flags |= SIGN;
            case 'u':
                str = number(str, va_arg(args, unsigned long), 10,
                        field_width, precision, flags);
                break; 
            
            case 'n':
                ip = va_arg(args, int *);
                *ip = (str - buf);
                break; 
	            
            default:
                if (*fmt != '%')
                    *str++ = '%';
	               
                if (*fmt)
                    *str++ = *fmt;
                else
                    --fmt;
                break;
        }
    }
	
    *str = '\0';
    return str-buf;
}
